The present invention relates generally to chemical processing of materials in industry and particularly to individual steps involved in the overall processes used in the chemical processing industry, particularly in industries involved in the separation of different materials from each other. More particularly, the present invention relates to improvements in chemical processing of two or more dissimilar materials where the dissimilar materials are to be separated from each other either in the one step or in different steps. Even more particularly, the present invention relates to a mixing step as a pretreatment or to improvements in the mixing step of an overall process of separating two or more different materials from each other, particularly two or more substantially immiscible fluids or fluids which can be separated on the basis of one or more properties or characteristics possessed by the individual fluids, such as their respective densities. The present invention finds particular application in methods and apparatus using hydrocyclones to mix two fluids together as a pretreatment step as one of the steps in the overall process of separating two different materials, such as oil or oil-like material and water from each other, and optionally separating suspended solid particles from the fluid in which the particles are suspended, typically water. However, the apparatus and method of the present invention may also be used as a mixer to incorporate one material into another material where there is to be no or substantially no separation of the two materials, such as for example, where a gas is to be incorporated into a liquid either temporarily or permanently, such as for example a carbonated beverage.
Although the present invention will be described with particular reference to the use of a hydrocyclone to mix air with waste water containing petroleum derived contaminants such as oils and lubricants or wastes from the food processing industry, such as dairy products, by forming an emulsion or similar mixture as a result of mixing the air and water under shearing conditions, it is to be noted that the present invention is not limited in scope to the described embodiment, but rather the scope of the present invention is more extensive so as to include other arrangements of the apparatus, other uses of the apparatus and methods, and application of the apparatus and methods in industries other than the oil or petroleum industry or food processing industry. Examples of the other industries in which the present invention finds particular application include the food industry generally, and the beverage industry in particular, including the fresh fruit juice industry and dairy industry.
Hydrocyclones have conventionally been used in the chemical processing industry to separate two dissimilar materials either two immiscible liquids, or solids and liquids, particularly suspended solids in liquids, from each other. In the past, hydrocyclones have been used to separate the two components of the mixture being treated on the basis of one or more properties or characteristics possessed by one or other of the components so that each component could be discharged separately through selected outlets of the hydrocyclone. Typically, the two components have been separated on the basis of their different specific gravities or densities. Feed containing the components to be separated is introduced into the hydrocyclone at or towards the top of the hydrocyclone and mostly spirals down the body of the hydrocyclone where it is discharged from an outlet located at the base of the hydrocyclone (the underflow) while the lower density component moves into a centrally located vortex created internally within the hydrocyclone body and is drawn out of another outlet which is located at the top of the hydrocyclone by the lower pressure developed in the hydrocyclone. Thus, to date hydrocyclones have always had two different outlets for different outlet streams and have been used to separate materials.
The present inventor has most surprisingly discovered that hydrocyclones can also be used to mix different materials together to achieve beneficial results rather than merely to separate the materials. One of the beneficial results of using the hydrocyclone as a mixer is to aid or facilitate subsequent processing of the materials by either maintaining the different materials as a mixture or separating the different materials in the mixture from each other. Furthermore, it has been surprisingly discovered by the present inventor that in an overall process of separating two or more different materials, if a hydrocyclone is used to mix the different materials together as a pretreatment before the actual separating process begins, the materials are more readily separated in the subsequent processing, or conversely, may form a better or more long-lasting mixture that can assist in the subsequent separation of the materials than if the pretreatment is not used.
Even more particularly, it has surprisingly been discovered by the inventor that introducing air or a gas into the mixture prior to the mixture entering the hydrocyclone greatly assists in the subsequent separation of the two dissimilar materials from each other than if air or gas is not used, even though the two materials are more intimately mixed together before any separating process or steps are commenced. It is totally unexpected that by more intimately mixing the components of a mixture, the components can be more readily separated from each other.
The method and apparatus of the present invention find application in chemical processing industries as diverse as the petroleum industry, such as in applications like oil field production water separation, refinery process water separation, petrochemical waste water separation and ballast water separation, in the food and beverage industries, such as for example separating waste from water in the dairy industry or beverage production industry, or mixing gases such as carbon dioxide with drinks such as beer or soft drinks, or in any industry requiring mixing of and/or separation of two dissimilar materials such as immiscible fluids, separation of two or more fluids of different densities or gravities, separation of solids or suspended solids from liquids and aeration or gasification of fluids. The types of materials in the petroleum industry which may be treated by the apparatus and method of the present invention include light hydrocarbons, heavy hydrocarbons, lubricants, fatty oils and fats, miscellaneous oil materials and the like.
According to the present invention there is provided a method of mixing a first material and a second material using a mixing apparatus wherein the first material comprises a mixture of two dissimilar components, in order to facilitate separation of the two dissimilar components from each other, characterised in that the first material is introduced into the mixing apparatus through a first inlet, the second material is introduced through a second inlet, the mixing apparatus is operated in such a manner that the second material is drawn into the mixing apparatus along with the first material so that mixing of the first and second materials occurs under conditions of shear to form an intimate mixture of the first and second materials, and the intimate mixture is discharged from the mixing apparatus, whereby separation of the two dissimilar components of the first material is facilitated by forming the intimate mixture of the first and second materials.
According to another aspect of the present invention there is provided a mixing apparatus for forming an intimate mixture of a first material and a second material wherein the first material comprises a mixture of two dissimilar components, characterised in that the apparatus comprises a first inlet means for admitting the first material to the mixing apparatus, a second inlet means for admitting the second material, a mixing chamber for forming an intimate mixture of the first and second materials under conditions of shear, and an outlet means for discharging the intimate mixture of the first and second materials, whereby separation of the two dissimilar components of the first material from each other is facilitated by the formation of the intimate mixture of the first and second materials.
According to another aspect of the present invention the apparatus may be used to form a more or less stable mixture of two dissimilar components where the mixture separates into the two components over a prolonged period of time or remains as an intimate mixture for a substantial period of time.
Typically, the first material is water or an aqueous solution or the like. Typically, the second material is a gas, such as air, nitrogen, oxygen, natural gas or the like.
Typically, the first material is a waste water mixture comprising water and oil or an oil-like or oleophilic material as the two dissimilar components. Typically, the first material is a beverage such as a soft drink, beer or the like. More typically, the aeration or gasification of the contaminated waste water facilitates separation of the oil or oil-like component from the water by the oil being entrained or otherwise associated with the air bubbles or gas bubbles formed from mixing the air or gas with the waste water under conditions of shear in the apparatus of the present invention. More typically, the beverage is gasified by the introduction of air or carbon dioxide to form an aerated or gasified drink under pressure.
Typically, the mixing apparatus is a hydrocyclone or hydrocyclone-like arrangement. More typically, the hydrocyclone is provided with an inlet. Even more typically, the inlet is the only inlet of the hydrocyclone. More typically, the two materials are premixed before entering the hydrocyclone.
Typically, the second inlet is located in a conduit leading to the hydrocyclone. More typically, the conduit is for conveying the waste water to the inlet of the hydrocyclone. Even more typically, the inlet is an air injection port, venturi or the like located in the conduit so that air or gas is mixed with the waste water prior to it entering the hydrocyclone arrangement. More typically, a mixture of gas/air and water enters the hydrocyclone where it is further mixed under conditions of shear to form an intimate mixture of entrained air or gas bubbles in the waste water. Typically, the amount of air admitted is controlled by a control means located in the conduit in the vicinity of the air inlet.
Typically, the amount of air/gas admitted to and mixed with the waste water is from about 1% to 50% by volume, more typically about 10% to 355% by volume, and even more typically 20% to 30% by volume, based on the total volume of the mixture.
Typically, the outlet means discharges the intimate mixture of gas/air bubbles and waste water to a conduit where it can be conveyed to a further processing step or stage. In the intimate mixture, the oil contaminants are associated with the gas or air bubbles for easier separation in a further processing step. More typically, the amount of air or gas bubbles is greater than the amount of oil or oil-like material to be separated from the waste water.
The hydrocyclone when used in the method and apparatus of the present invention does not do any separating itself, but rather xe2x80x9cdrawsxe2x80x9d air, typically at the suction side of a positive displacement pump, into the conduit leading to the hydrocyclone, dissolving the air and mixing it well with the waste water. The result is the formation of millions of tiny air bubbles which can entrain oil droplets, suspended solid particles or the like, so that the air bubbles can then bring the suspended solids or droplets to the surface during subsequent processing to assist in separation of these materials from each other. Without the hydrocyclone as a mixer in the pretreatment step there is a non-uniform distribution of air bubbles and large slugs of air which leads to less satisfactory separation of the two dissimilar components of the waste water.